Seeds, such as flax, chia, hemp and sesame seeds, are economically valuable and nutritious food products. However, there are many potential points of entry for pathogens in the seed processing chain between harvesting and packaging. Some pasteurized seeds are commercially available. However, pasteurizing cooks the seeds and is not an option for seeds that are marketed as raw. The seeds are believed to have more nutritional value when raw, and raw seeds are at preferred by at least some consumers.
Some raw fruits and vegetables have been sanitized with aqueous compositions. For example, U.S. Pat. No. 2,512,640 describes the use of peracetic acid (also known under the tradename Peracid) for the treatment of raw fruits and vegetables to reduce spoilage from bacteria and fungi before processing. Peracetic aqueous solutions have also been suggested to control pathogenic organisms on growing plants (International Patent Publication WO 2012/051699 and U.S. Pat. Nos. 6,024,986; 6,165,483; and, 6,238,685).
As a consequence of their small size, however, seeds have a much larger surface area for a given volume than most fruits and vegetables. Aqueous sanitizing solutions generally employ a contact killing mechanism and so efficacy depends on coverage. This suggests that a large volume of any aqueous composition would be required to treat seeds, but seeds are typically stored and processed dry.
Some seeds also release mucilage when wet. Mucilage is a polysaccharide with a high swelling index that produces a viscous solution in water. Mucilaginous seeds contain mucilage-secreting cells (MSCs) primarily located in the seed coat, or epidermal layer of the seed. When the seeds are dry, the mucilage is contained in cell wall structures, for example between primary and secondary cells walls. When the seeds contact water, the mucilage swells, breaks free of the cell structures, and covers the seeds with mucilage. The mucilage is edible but, if secreted, it binds the seeds together making the seeds difficult to process and store. Examples of commercially important mucilage producing seeds include flax and chia.
Current food safety practices for raw seeds rely on sampling. When sampling detects an excess of pathogens, large containers of seed are wasted. And yet sampling also fails to detect all contaminated shipments. For example, sesame, chia and flax seeds have all caused outbreaks of Salmonella poisoning among people eating the raw seeds.